Acrylamide has many applications, such as flocculating agents, petroleum recovering agents, paper strength enhancers in the papermaking industry, and thickeners for papermaking, and is a useful substance as a raw material for polymers.
Among industrial processes for acrylamide production, formerly used is the sulfuric acid hydrolysis process which comprises the step of heating acrylonitrile together with sulfuric acid and water to obtain acrylamide sulfate salts. This process has then been replaced with the copper-catalyzed process in which acrylonitrile is hydrated in the presence of a copper catalyst (e.g., metal copper, reduced copper, Raney copper, etc.) to obtain acrylamide. In recent years, as a production process with fewer by-products, industrial production has also been conducted by the microbial process in which acrylamide is obtained by means of microbially-derived nitrile hydratase.
As in the case of many unsaturated monomers, acrylamide is easy to polymerize by the action of light or heat and also has the property of very easily polymerizing upon contact with the surface of iron, so that acrylamide has been difficult to stably handle while suppressing its polymerization during each step of its production and during its storage/keeping.
For this reason, various stabilizers have been proposed to stabilize acrylamide. Examples of these stabilizers include thiourea, ammonium rhodanide, nitrobenzol (Patent Document 1), ferron (Patent Document 2), furil dioxime (Patent Document 3), cyanide complex compound of chromium (Patent Document 4), p-nitrosodiphenylhydroxyamine (Patent Document 5) and so on.